Recirculating pilot and burner



June 9 w. H. GILMORE ET AL 2,748,847

' RECIRCULATING PILOT AND BURNER Filed May 6, 1952 3 Sheets-Sheet 1 l2 oooooooouoooooooooooooooo ooo 00000000000000 4' FIG. I a

INVENTOR FIG. 5 WILLIAM H. GILMOR MQLEMENT R. GILMORE ATTORNEYS June 1956 w. H. GILMORE ET AL 2,748,847

RECIRCULATING PILOT AND BURNER 3 Sheets-Sheet 2 Filed May 6, 1952 FIG. 3

FIG. 4

INVENTORS WILLIAM H. GILMORE CBE EMENT R. GILMORE I I NW FIG. 2

ATTORNEYS J 1956 w. H. GILMORE ET AL 2,748,847

RECIRCULATING PILOT AND BURNER Filed May- 6, 1952 5 Sheets-Sheet 3 1N VEN TORS WILLIAM H. GILMORE CLEMENT R. GILMORE BY A ATTORNEYS United States Patent RECIRCULATIN G PILOT AND BURNER William H. Gilmore, Columbus, and Clement R. Gilmore, Shaker Heights, Ohio, assignors, by direct and mesne assignments, to East 134 Company, Cleveland, Ohio, a corporation of Ohio Application May 6, 1952, Serial No. 286,302

9 Claims. (Cl. 158-91) The present invention relates to vaporizing oil burners and particularly to means to attain a very high turndown ratio with efiicient combustion at both high and low stages of burner operation.

In many oil heating installations it is impractical to provide for automatic ignition of a cold burner at the initiation of each heating run because of the necessity for accessory igniting equipment and because of the typically slow responsive rise of vaporizing burners to full fire after ignition. These difliculties are frequently avoided by providing for maintenance of a pilot fire in the burner during shutdown of the normal fire. The pilot fire keeps the burner warm and furnishes a constantly hot ignition means.

To obtain any degree of over-all efficiency of a burner employing a pilot fire, fuel consumption during pilot fire operation must be a small fraction of that at full or normal fire operation, i. e., the turndown ratio must be high. In burners employing certain kinds of fuel there is no difficulty in obtaining a very high turndown ratio. The high turndown ratio possible in a gas burner, for instance, has led to the almost universal employment of constantly burning pilot flames in domestic gas furnaces and cooking ranges.

In the past, the attainable turndown ratio in vaporizing oil burners has been limited because of the relatively narrow range from minimum fire to full fire operation in these burners. The heat necessary to initiate and maintain vaporization of the fuel oil within a retort or vaporization chamber of given size requires, in turn, a high minimum level of operation. Some increase in the turndown ratio of vaporizing burners has been attained by providing what are in efiiect segmented subdivisions of the vaporization chamber in which a reduced amount of total vaporization may occur. However, the somewhat increased turndown ratio still has not been high enough for over-all efficiency and partitioning of the retort chamber hasled to smoking and popping or snap-back as the burner flame hunts between partitioned chambers during initial firing when the burner is cold.

In addition to the advantages of a high turndown ratio from the point of view of over-all burner efliciency, possible operation at a very low pilot stage is advantageous with respect to the problem of automatic initial burner ignition. The role of a very low stage pilot in aiding the initiation of full fire combustion in a vaporizing oil burner is analogous to that of kindling wood in starting a bonfire; a small ignition coil canquickly light a pilot fire which in turn will rise to full fire, but in general prohibitively large, costly and slow acting ignition equipment is required to light the burner directly or to light a relatively high capacity pilot fire.

Previous partitioned pilot burners have tended to candlewick or build up small carbon deposits within the pilot chamber which occasionally produce objectionable smoking. Of particular importance is the fact that prior burners have been incapable of burning 'so-called catalytic or cat-cracked oil, the pilot chambers forming heavy carbon deposits after several hours of operation with this type of fuel.

We have provided a vaporizing oil burner in which the attainable turndown ratio is much greater than that of previous vaporizing burners. Furthermore, we have provided a vaporizing oil burner which may be readily ignited by an electric ignition coil to induce self-supporting combustion almost instantaneously and which is of less expensive construction in relation to maximum burner capacity than has ever heretofore been possible. Our burner will cleanly and completely burn catalytic oil during both pilot fire and higher stages. Our burner has no tendency to Candlewick.

Other objects and advantages of our invention will be- I come apparent from an examination of the following specifications and the accompanying drawings in which:

Figure 1 is an elevational view in cross section of a burner embodying the invention.

Figure 2 is a side view of the pilot chamber structure taken from line 2-2 in Figure 1.

Figure 3 is a top view partially in cross section taken on line 33 in Figure l.

Figure 4 is a side view of the pilot chamber taken from line 44 in Figure 5 and viewing the pilot chamber structure from a different direction than that from which it is viewed in Figure 2.

Figure 5 is a top view of the pilot chamber structure.

Figure 6 is a view similar to Figure 1 showing a burner employing a metering barrier around the entire periphery of the ring comprising the several ring segments described herein.

In the particular embodiment of the invention shown, an oil burner comprises an outer housing 10, a retort chamber 11 and a flange 12 defining a jacket chamber 13. Air is supplied to the chamber through the inlet aperture 14. The wall of the chamber is provided with a plurality of air inlets or ports 15 admitting air from the jacket chamber 13. To more fully utilize the high capacity of the burner, air introduced through the inlet aperture 14 will preferably be under forced draft through use of a suitable fan or air pump (not shown).

The lower row of air inlets 15 is preferably slanted downwardly as illustrated to cause incoming air to be directed between a slotted vertical stack 20 and a ring 21 which is held in spaced relation from the stack by suitable short supporting arms 22 or other equivalent means. Supported on the upper end of the stack 20 is a stack cover 23. As may be seen in Figure 3, segments of approximately degrees are eliminated from the stack 20 and the ring 21 to accommodate the pilot chamber structure described below.

The pilot chamber structure comprises a hood 40 which, when in position in the bottom of the retort or vaporizing chamber 11, defines a pilot chamber 41 between the underside of the hood and the adjacent portions of the side and bottom of the vaporizing chamber 11. The outermost end of the hood is of a height greater than that of the lowermost row of air inlet holes 15, so that certain of these holes, P, discharge into the pilot chamber. The top wall 42 of the hood 40 may, as illustrated, consist of a segment of the surface of an inverted, shallow truncated cone. The top outside edge 43 of the wall 42 is arcuate and extends along the arcuate inner surface of the wall of the chamber 11. A notch 44 is cut in the edge 43 to permit a substantial gas flow to occur upwardly along the Between the vertical sidewalls 45 of the hood 40 extends an arcuate segment 46 which, at full fire, functions as a continuation ofthe ring 21. The segment 46 is preferably slanted outwardly and upwardly with a depending lip 47 formed on its outer edge. The segment 46 is positioned so that its long transverse cross section aims at the approximate vertical mid-point of the arcuate opening 48 defined at the inner end of the hood 40 by the topwall 42 and the sidewalls 45, as may be clearly seen in Figure l.

Fuel oil is supplied to the burner through a pipe 50 which extends through the outer housing and into the pilot chamber portion of the vaporizing chamber 11. The flow of fuel is controlled by a valve mechanism (not shown) which is of any suitable construction which will meter the flow of oil at selected rates.

In operation, oil initially admitted to the burner may be ignited manually by means of a lighter tube (not shown) or by momentarily lifting the stack cover 23 and dropping a piece of burning paper or other material into the stack. An alternative means of ignition particularly adapted to forced draft burners is the provision of an electric hot coil at the open end 48 of the pilot chamber. In either case, within a short period after ignition, a recirculating gas-air flow is induced around the segment 46 as illustrated by the arrows in Figure 1. Incoming air from the ports P is continuously tangentially supplied to this path of circulation. Oil vapors swept off the oilwetted bottom of the pilot chamber are also continuously supplied to the circulating gases. A steady hot smokeless flame occurs along this circular path.

As the rate of oil supply is increased for higher stage operation, the oil vapor-air mixture becomes too rich to support combustion and the combustion zone moves out past the opening 48 and the notch 44. Air from ports other than the ports P begins to support combustion as this outward movement of the flame occurs. As the rise to full fire continues, oil vapor-air circulation and intimate intermixture begins to occur around portions of the ring and finally around the entire ring. The flame front thereupon rises in the burner until at high fire the flame occurs at and above the highest row of ports 15.

Although the above described performance of our burner during the rise to full fire is fully satisfactory under practical conditions, there may occasionally be a tendency for the flame to snuff out at various angular portions of the ring 20 as combustion begins to occur around this ring. This produces a very slight amount of undesirable smoking. This tendency to slight smoking at this stage of operation may be remedied by providing an outsidc depending lip (not shown) on the ring 21 similar to the lip 47.

The housing or hood 42 effects segmentation of the lower portion of the pot chamber 11 to aid in obtaining a high turndown ratio. In inexpensive burners designed to be produced at low unit cost and where pilot operation is desirable but a high turndown ratio is not critical, the burner illustrated in Figure 6 may be utilized. In general organization this burner is similar to the one illus trated in the other figures. Here, however, the hood 42 has been eliminated and the ring 21-A made continuous. A lip 47A is provided around the entire circumference of the ring 21-A. This burner will provide a smokeless low fire or pilot stage, however operation at this pilot stage will involve a greater fuel consumption than will pilot operation of the burner illustrated in Figures 1 to 4.

As suggested earlier, previous partitioned burners have been provided with the object of providing low capacity pilot fire operation, but these partitioning arrangements have been objectionable because of the tendency of the flame to hunt and to snap back and forth past the partition when the cold burner is ignited. Our principle of establishing circulatory movement within the pilot chamber not only provides for lower capacity pilot operation at a given pressure than that heretofore attainable, but

it greatly increases the stability of the flame during transitory stages so that the above objectionable features are eliminated.

It is to be noted that the richness of the circulating mixture within the pilot chamber 41 is a function both of the velocity of circulation around the segment 46 (with which varies the intensity of the sweeping action of the recirculating air-gas over the oil film on the chamber bottom) and the rate of air inflow through the ports I, so that a balance between these two variables must be maintained in order not to snuff out the fire during pilot operation or at the initiation of the rise from pilot to high stage operation. Fora given velocity of circulation, too high an air inflow will produce an over-lean mixture while too low an air inflow will cause an over-rich mixture causing the fire to tend to snuff out in either case. Although within a short time increment after variation of air inflow circulation velocity also varies to restore the proper balance, nevertheless the unbalance existing momentarily due to the inertia of the circulating gases may cause the fire to snuff out.

Although it would appear that to reduce the inertia effect of the circulating gases by streamlining their path of circulation would overcome the above problem, we have discovered that the solution lies in almost a diametrically opposite arrangement. We have deliberately placed a barrier, the lip 47, in the path of circulation. The lip 47 apparently acts as a metering gate or mixture accumulator. It is believed that upon a sudden inflow of air through P (due to natural draft fluctuations or the increase of forced draft due to pressure control limitations or incident to the rise from normal fire), the circulating mixture becomes instantaneously over-lean, but a quantity of adequately rich mixture momentarily detained in the inner corner defined by the metering barrier or lip 47 spills around the lip and supplies suflicient oil vapor to support combustion until circulation velocity adjusts to the increased air inflow. Conversely, upon a sudden drop in inflow through P, the circulating mixture becomes instantaneously over-rich, but a quantity of adequately lean mixture spills around the lip 47 and contains sufficient air to support combustion until the inertia of the circulating gases is overcome. The lip 47A functions similarly to control the fuel-air ratio of gases circulating around the ring 21A in the path illustrated by the arrows in Figure 5.

Metering barriers 47 or 47-A not only overcome the snuffing out problem outlined above, but they further promote stability of the fire throughout the early stages of the rise to full fire by making variations in the fuelair ratio of the circulating mixture less responsive to fluctuations in draft.

The illustrated segment 46 and the lip 47 extend horizontally from one sidewall 45 to the other. In some larger installations, superior metering action is obtained by depressing the center portions of the segment and lip a distance equal to about 10 to 20 percent of the segment length. This arrangement improves the rapidity and smoothness of reserve mixture spill over the lip in response to variation in air inflow. It is also preferable to provide slots and gaps 60 in the stack 20 to provide for fullest recirculation of oil vapor-air mixtures in the lower portions of the vaporizing chamber 11.

Other variations in the invention we have disclosed will occur to those familiar with vaporizing burners and, accordingly, the scope of our invention is not limited to specific embodiments disclosed, but is to be defined solely by the following claims.

In the following claims the terms longitudinally and radially are to be understood as used in reference to the recited pot as a whole rather than in reference to the hood or pilot chamber Within the pot.

What is claimed is: p

1. In a burner, a pot having base and side walls, said pot side walls having longitudinally spaced air-admitting ports, a hood comprising hood side walls disposed in the base portion of said pot and a cojoining wall between said hood side walls and spaced from said base wall of said pot by said hood side walls to form a pilot chamber having an outlet facing toward the central base portion of said pot and open-ing into the pot proper, fluid fuel feed means having :a discharge end communicating with the interior of said pilot chamber, the radially outward edges of said hood side walls and said cojoining wall lying along said side walls of said pot a longitudinal distance such that some of said longitudinally spaced airadmitting ports open into said pilot chamber, a notch in said radially outward edge of said cojoining wall of said hood to form an .alternate path of communication between said pilot chamber and said pot proper adjacent said pot side wall, a ring segment extending within said pilot chamber between said hood side walls and having a radially outward lip which depends longitudinally toward said base wall of said pot, a ring segment extending without said pilot chamber from one to the other of said hood side walls, both said segments being centered approximately on the axis of said pot.

2. In a burner, a pot having base and side walls, said pot side walls having longitudinally spaced air-admitting ports, a hood comprising hood side walls disposed in the base portion of said pot and a cojoining wall between said hood side walls and spaced from said base wall of said pot by said hood side walls to form a pilot chamber having an outlet facing toward the central base portion of said pot and opening into the pot proper, fluid fuel feed means having a discharge end communicating (with the interior of said pilot chamber, the radially outward edges of said hood side walls and said cojoining wall lying along said side walls of said pot, a notch in said radially outward edge of said cojoining wall of said hood to form an alternate path of communication between said pilot chamber and said pot proper adjacent said pot side wall, a ring segment extending within said pilot chamber between said hood side walls, a ring segment extending without said pilot chamber from one of said hood side walls, to the other, both said segments being centered approximately on the longitudinal axis of said pot.

3. In 'a fluid fuel burner, a pot having a circumferential side wall and a base wall, a fluid fuel feed pipe extending into the interior of said pot adjacent said base wall, a pilot housing in said pot defining a pilot chamber in com- -munication with the discharge end of said feed pipe, said pilot chamber comprising radially inwardly converging pilot chamber side walls and a radially and longitudinally inwardly inclined pilot chamber transverse wall, the radially inward edges of said pilot chamber walls defining a first relatively restricted discharge opening into that portion of the pot interior not occupied by said pilot chamher, said transverse wall being spaced from said circumferential pot side wall to define a second relatively restricted discharge opening into said portion of the pot interior, a ring segment extending within said pilot chamber between said pilot chamber side walls, a flange depending longitudinally inwardly from the radially outward edge of said ring segment, a plurality of air inlet ports circumferentially spaced about said pot side wall at varying longitudinal locations, at least one of said ports registering with said pilot chamber.

4. -In a fluid fuel burner, a .pot having a circumferential side wall and a base wall, a fluid fuel feed pipe extending into the interior of said pot adjacent said base wall, a pilot housing in said pot defining a pilot chamber in communication with the discharge end of said feed pipe, said pilot chamber comprising radially inwardly converging pilot chamber side walls and a radially and longitudinally inwardly inclined pilot chamber transverse wall, the radially inward edges of said pilot chamber walls defining a first relatively restricted discharge opening into that chamber, a portion of the radially and longitudinally outward edge of said pilot chamber transverse wall being walls, a second ring segment extending within said portion of the pot interior from one pilot chamber side wall to the other, a plurality of air inlet :ports circumferentially spaced about said pot side wall at varying longitudinal locations, and at least one air inlet port in a wall of said pot and registering with said pilot chamber.

5. In a fluid fuel burner, a pot comprising side and bottom walls, a hood forming a pilot chamber comprising two hood side walls extending from a side wall of said pot inwardly and along the bottom wall of said pot, fluid fuel feed means having a discharge end communicating with the interior of said pilot chamber, the lower edges of said hood side walls engaging with the bottom wall of said pot, the inner end portions of said hood side walls converging, and a hood top wall extending inwardly and downwardly toward the horizontal center of said pot and connecting said hood side walls, a peripheral portion of the outer upper edge of said hood top wall being in apposition to but spaced from said pot side wall, a first ring segment extending within said pilot chamber between said hood side walls, a second ring segment extending without said pilot chamber from one to the other of said hood side walls.

6. In a fluid fuel burner, a pot comprising side and bottom walls, a hood forming a pilot chamber comprising two hood side walls extending from a side wall of said pot inwardly and along the bottom wall of said pot, fluid fuel feed means having a discharge end communicating with the interior of said pilot chamber, the lower edges of said hood side walls engaging with the bottom wall of said .pot, the inner end portions of said hood side walls converging, and a hood top wall extending inwardly and downwardly toward the horizontal center of said pot and connecting with hood side walls, a peripheral portion of the outer upper edge of said hood top wall being in apposition to but spaced from said pot side wall, a first ring segment having a depending lip formed on its outer edge and extending within said pilot chamber between said hood side walls, a second ring segment extending without said pilot chamber from one to the other of said hood .side walls.

7. In an oil burner, a vaporizing pot having a circumferential side wall and a bottom wall, a pilot chamber within said pot and defined by a hooded, wall structure lying on said pot bottom wall alongside said pot side wall at one portion of the circumference of said pot side wall, fluid fuel feed means having a discharge end communicating with the interior of said pilot chamber, the height of said hooded, wall structure being less than half the height of said pot, said pilot chamber tapering radially inwardly and terminating at its inner end in a first opening communicating with the remainder of the pot interior adjacent said pot bottom wall, a second opening communicating bet-ween said pilot chamber and said remainder of the pot interior adjacent said one portion of the circumference of said .pot side wall, a ring segment extending above said pot bottom wall within said chamber from one side of said hooded, wall structure to the other, a plurality of air ports in said pot side wall, at least one of said .ports opening into said pilot chamber and the remainder of said ports opening into said remainder of the pot interior.

8. In an oil burner, a vaporizing pot having a circumferential side wall and a bottom wall, a pilot chamber within said pot and defined by a hooded, wall structure lying on said pot bottom wall alongside said pot side wall at one portion of the circumference of said pot side wall, fluid fuel feed means having a discharge end communicating with the interior of said pilot chamber, the height of said hooded, wall structure being less than half the height of said pot, said pilot chamber tapering radially inwardly and terminating -at its inner end in a first opening communicating with the remainder of the pot interior adjacent said pot bottom wall, a second opening communicating between said pilot chamber and said remainder of the pot interior adjacent said one portion of the circumierence of said pot side wall, a ring segment extending above said pot bottom wall within said chamber firom one side of said hooded, wall structure to the other, a second ring segment extending above said pot bottom wall within said remainder of the pot interior from one side of said hooded, wall structure to the other, a plurality of air ports in said pot side wall, some of said ports opening into said pilot chamber and the remainder of said ports opening into said remainder of the pot interior.

9. In a fluid fuel burner, a pot comprising side and bottom walls, a hood forming a pilot chamber comprising two hood side walls extending from a side Wall of said pot inwardly and along the bottom wall of said pot, fluid fuel feed means having a discharge end communicating with the interior of said pilot chamber, the lower edges of said hood side walls engaging with the bottom wall of said pot, the inner end portions of said hood side walls converging, and a hood top wall extending inwardly and downwardly toward the horizontal center of said pot and connecting said hood side walls, and a ring segment extending within said pilot chamber between said hood side walls, the cross sections of segments of said ring having greater width than depth, said ring being spaced from said side wall of said pot and from said hood top wall and from said bottom wall of said pot, and means to introduce air into said .pilot chamber through said side wall of said pot tangentially to paths around said cross sections.

References Cited in the file of this patent UNITED STATES PATENTS 2,339,637 Hayteir Jan. 18,1944 2,474,530 Huston June 28, 1949 2,476,871 Huston July 19, 1949 2,490,267 Hayter et a1. Dec. 6, 1949 2,537,966 Cargile et al Jan. 16, 1951 2,574,358 St. John Nov. 6, 1951 

